Hydroplaning is characterized by the momentary presence of an amount of water between the ground making up the road and the part of a tire tread in contact with the ground. During hydroplaning, the film formed by the presence of water prevents all or some of this part of the tire tread from contacting the ground, and therefore there is no longer any grip and consequently any transfer of loads between the vehicle and the ground.
A film of water between all or some of the tire tread in contact with the ground is formed when the flow of water circulating between these two surfaces becomes greater than the flow of water that can be removed simultaneously by the roughness of the ground and the pattern of the tire tread. This saturation effect is dependent on the height of water present on the ground and the speed of the vehicle.
The consequences of hydroplaning, during an acceleration by application of a driving force, during a deceleration by application of a braking force, or during a change in direction, are considerable and may involve a partial or complete loss of control of the vehicle. It is therefore of paramount importance when travelling on wet ground to be able to anticipate the conditions for hydroplaning.
To the driver of the vehicle, no warning sign precedes the onset of partial or complete hydroplaning—the danger is sudden and cannot be foreseen.
It is known from U.S. Pat. No. 5,502,433 to detect a risk of hydroplaning based on measurements of shear stresses of a block of the tire tread in an area of contact of the tire tread and the ground.